HIROSHIMA, JAPAN - A powerful tsunami triggered by a massive earthquake devastated the northeastern coast of Japan on Friday, leaving hundreds dead and launching waves that triggered warnings from Alaska to South America.

The Japan Meteorological Agency said the 8.9-magnitude earthquake was the strongest in the country's history. Television footage showed towering waves surging toward the northeastern shoreline, pulling cars into the water and knocking boats and buildings onto their sides.

Initial forecasts warned of potential devastation throughout the Pacific Rim, including Hawaii, and reaching east around the globe to the continental United States. But the waves that reached Hawaii about 8 a.m. Washington time were relatively modest, and officials said the tsunami would have minimal impact on the West Coast.

Japan's Kyodo News agency said between 200 and 300 bodies were found near Sendai, the capital of Miyagi Prefecture and the population center nearest the epicenter of the quake.

The agency later reported that the death toll was likely to surpass 1,000.

Early Saturday, a 6.6 magnitude earthquake on a different fault line in central Japan caused buildings to sway in Tokyo, the Associated Press reported. The U.S. Geological Survey recorded two quakes Saturday near the west coast of Honshu, Japan's main island. It said a 6.2 magnitude quake about 121 miles northwest of Tokyo was followed less than an hour later by a 6.6 temblor 331 miles north of the capital.

In Washington, President Obama said he was "heartbroken" by the tragedy and offered "whatever assistance is needed."

Speaking about 12 hours after the quake struck, Obama said the United States has not suffered "any major damage so far" from the resulting tsunami. But waves that struck northern California near the Oregon border later swept four people out to sea, damaged three dozen boats and wrecked the harbor of Crescent City, Calif. One of the four victims - a man who was pulled out to sea while photographing the tsunami - was missing and feared dead, and the Coast Guard was searching for him, news services reported.

Damage was also reported to fishing boats and wooden docks in Santa Cruz on the central California coast.

Although thousands of people fled their homes along the California coast, scientists said the main thrust of the tsunami was to the southeast, across the Pacific toward South America. As a result, Chile upgraded a tsunami alert Friday and braced for impact later in the day.

In Japan, houses floated like rafts along the waves when the tsunami hit. In some areas, the wall of water looked more like a black shroud of sludge and debris, consuming a vast, flat patchwork of farmland. About eight hours after the quake, officials told the news service that they had lost contact with at least one train traveling in that area, and a ship carrying at least 100 people was said to have been swept out to sea.

The national police agency confirmed 137 deaths, news services reported, with officials saying that number was sure to rise as emergency workers gained access to the hardest-hit areas.